请问下面这个方法的功能是什么呢，求大神指导？

#include
#include
#include
using namespace std;
#define ll long long
//返回以数字k开头，<=n的数的个数
ll findKthNumber(ll n, ll k)
{
ll curr = 1;
k = k - 1;
while (k > 0)
{
ll steps = 0, first = curr, last = curr + 1;
while (first <= n)
{
steps += min(n + 1, last) - first;
first *= 10;
last *= 10;
}
if (steps <= k)
{
curr += 1;
k -= steps;
}
else
{
curr *= 10;
k -= 1;
}
}
return curr;
}